Final answer:
Cassie and Blaine's daughter has a 0% risk of being affected with hemophilia A because she will inherit only one X chromosome from her mother, who is a carrier, and one from her father, who has a normal X chromosome.
Step-by-step explanation:
Hemophilia A is a sex-linked recessive disorder, meaning it is carried on the X chromosome. Females have two X chromosomes while males have one X and one Y chromosome. Since hemophilia is a recessive trait, a female needs two mutated X chromosomes to be affected with hemophilia A, while a male only needs one because they have only one X chromosome.
In the scenario provided, Cassie's risk of carrying the hemophilia gene is high because her father, Blaine, has hemophilia A. Therefore, she must have inherited one mutated X chromosome from him. Seeing as her mother, Barbara, does not have hemophilia, her other X chromosome is likely normal. Thus, Cassie is a carrier but does not express the disease. Cassie and Blaine, both with a family history of hemophilia, have a son, Daniel, with hemophilia A. Considering Cassie's carrier status, if they have a daughter, she will either be a carrier like her mother or not have the gene mutation at all if she inherits her father's normal X chromosome.
According to the inheritance pattern of X-linked recessive disorders, the daughter's risk of being affected with hemophilia A is 0%. If she inherits the normal X chromosome from Blaine and the mutated one from Cassie, she will be a carrier, but not afflicted by the disease. If she inherits the normal X from both parents, she will neither be affected nor be a carrier. Therefore, the correct answer to the question is (A) 0%.